Major research project to detect gravitational waves is underway

A research project to detect gravitational waves, minute ripples in the fabric of space and that were predicted by Einstein, was officially launched on May 19, 2015.

The Advanced LIGO Project, a major upgrade in equipment that will increase the sensitivity of the Laser Interferometer Gravitational-wave Observatories instruments was opened at a ceremony on Tuesday, May 19, at the LIGO Hanford facility in Washington.

Gravitational waves are caused by cosmic catastrophes such as merging black holes, collapsing stars and supernovae and their detection will be the experimental validation of one of the fundamental predictions of Einstein’s Theory of General Relativity. The new upgraded detectors will also offers the potential to probe the earliest moments of the Universe just after the Big Bang, which are currently inaccessible.

Although they have not yet been detected directly, the influence of gravitational waves on a binary pulsar system - two neutron stars orbiting each other - has been measured accurately and is in agreement with the predictions. Scientists therefore have great confidence that gravitational waves exist. But a direct detection will confirm Einstein's vision of the waves and allow a fascinating new window into cataclysms in the cosmos.

LIGO was designed and is operated by Caltech and MIT with funding from the National Science Foundation (NSF). Advanced LIGO, funded by the NSF with important contributions from the UK Science and Technology Facilities Council (STFC), the Max Planck Society of Germany, and the Australian Research Council (ARC), as well as University of Birmingham physicists, is now being brought online with the first searches for gravitational waves planned for the Autumn of 2015.

Professor Alberto Vecchio, from the University of Birmingham’s School of Physics and Astronomy, said: ‘After over a decade of work, Advanced LIGO is the first instrument of a new generation of gravitational-wave detectors to come on-line. It will provide us with a radically new view of the Universe in an observational window that has remained completely untapped so far.’

Professor Andreas Freise, from the University of Birmingham’s School of Physics and Astronomy, said: ‘I am excited about the fast progress that is being made at both LIGO sites. The instruments are now in the final commissioning phase which shall lead to the official start of science observations at the end of this year.’

LIGO was originally proposed in the 1990s as a means of detecting gravitational waves. Each of the 4-km-long L-shaped LIGO interferometers (one at LIGO Hanford and one at the LIGO observatory in Livingston, Louisiana) use a laser split into two beams that travel back and forth down long arms which are beam tubes from which the air has been evacuated. The beams are used to monitor the distance between precisely configured mirrors. According to Einstein's theory, the relative distance between the mirrors will change very slightly when a gravitational wave passes by. The original configuration of LIGO was sensitive enough to detect a change in the lengths of the 4-km arms by a distance one-thousandth the size of a proton; Advanced LIGO, which will utilize the infrastructure of LIGO, will be 10 times more sensitive.

The new sensitivity will allow Advanced LIGO to look at the last minutes of the life of pairs of black holes as they spiral closer, coalesce into one larger black hole, and then vibrate much like two soap bubbles becoming one. Advanced LIGO will also be used to search for the gravitational cosmic background—allowing tests of theories about the development of the universe only 10-35 seconds after the Big Bang.

LIGO research is carried out by the LIGO Scientific Collaboration (LSC), a group of some 950 scientists at universities around the United States and in 15 other countries. The LSC network includes the LIGO interferometers and the GEO600 interferometer, a think tank and test bed for advanced detector techniques. GEO600 is located near Hannover, Germany, and designed and operated by scientists from the Max Planck Institute for Gravitational Physics and Leibniz Universität Hannover, along with partners in the United Kingdom funded by the Science and Technology Facilities Council (STFC). The LSC works jointly with the Virgo Collaboration, which designed and constructed the 3-km-long Virgo interferometer located in Cascina, Italy to analyze data from the LIGO, GEO, and Virgo interferometers.

UK scientists, in particular, members of the Advanced LIGO UK team at the Universities of Glasgow and Birmingham and the STFC’s Rutherford-Appleton Laboratories, have been centrally involved in the development, construction and, recently, commissioning of key elements of the Advanced LIGO detectors.

In addition to delivering sensors and electronics for the suspensions system, Birmingham scientists have developed and maintained one of the main simulation tools, FINESSE, that has contributed significantly to the design of the optical configuration and is used for the commissioning of the large interferometers.

Scientists at Birmingham, in collaboration with British and German partners of the GEO collaboration, and colleagues of the LIGO Scientific Collaboration have also played a central role in developing the data analysis techniques that will be used to capture the echoes of black hole and neutron star collisions in the Advanced LIGO data once the instruments start to operate later this year.